55 research outputs found
Preparing an unsupervised massive analysis of SPHERE high contrast data with the PACO algorithm
We aim at searching for exoplanets on the whole ESO/VLT-SPHERE archive with
improved and unsupervised data analysis algorithm that could allow to detect
massive giant planets at 5 au. To prepare, test and optimize our approach, we
gathered a sample of twenty four solar-type stars observed with SPHERE using
angular and spectral differential imaging modes. We use PACO, a new generation
algorithm recently developed, that has been shown to outperform classical
methods. We also improve the SPHERE pre-reduction pipeline, and optimize the
outputs of PACO to enhance the detection performance. We develop custom built
spectral prior libraries to optimize the detection capability of the ASDI mode
for both IRDIS and IFS. Compared to previous works conducted with more
classical algorithms than PACO, the contrast limits we derived are more
reliable and significantly better, especially at short angular separations
where a gain by a factor ten is obtained between 0.2 and 0.5 arcsec. Under good
observing conditions, planets down to 5 MJup, orbiting at 5 au could be
detected around stars within 60 parsec. We identified two exoplanet candidates
that require follow-up to test for common proper motion. In this work, we
demonstrated on a small sample the benefits of PACO in terms of achievable
contrast and of control of the confidence levels. Besides, we have developed
custom tools to take full benefits of this algorithm and to quantity the total
error budget on the estimated astrometry and photometry. This work paves the
way towards an end-to-end, homogeneous, and unsupervised massive re-reduction
of archival direct imaging surveys in the quest of new exoJupiters.Comment: Accepted for publication in A&
Direct discovery of the inner exoplanet in the HD206893 system. Evidence for deuterium burning in a planetary-mass companion
Long term precise radial velocity (RV) monitoring of the nearby star
HD206893, as well as anomalies in the system proper motion, have suggested the
presence of an additional, inner companion in the system. Here we describe the
results of a multi-epoch search for the companion responsible for this RV drift
and proper motion anomaly using the VLTI/GRAVITY instrument. Utilizing
information from ongoing precision RV measurements with the HARPS spectrograph,
as well as Gaia host star astrometry, we report a high significance detection
of the companion HD206893c over three epochs, with clear evidence for Keplerian
orbital motion. Our astrometry with 50-100 arcsec precision afforded
by GRAVITY allows us to derive a dynamical mass of 12.7 M and an orbital separation of 3.53 au for HD206893c. Our
fits to the orbits of both companions in the system utilize both Gaia
astrometry and RVs to also provide a precise dynamical estimate of the
previously uncertain mass of the B component, and therefore derive an age of
Myr. We find that theoretical atmospheric/evolutionary models
incorporating deuterium burning for HD206893c, parameterized by cloudy
atmospheres provide a good simultaneous fit to the luminosity of both HD206893B
and c. In addition to utilizing long-term RV information, this effort is an
early example of a direct imaging discovery of a bona fide exoplanet that was
guided in part with Gaia astrometry. Utilizing Gaia astrometry is expected to
be one of the primary techniques going forward to identify and characterize
additional directly imaged planets. Lastly, this discovery is another example
of the power of optical interferometry to directly detect and characterize
extrasolar planets where they form at ice-line orbital separations of 2-4\,au.Comment: Accepted to A&
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